Anion exchange reaction

The anion-exchange reactions of ionic liquids can really be divided into two distinct categories direct treatment of halide salts with Lewis acids, and the formation of ionic liquids by anion metathesis. These two approaches are dealt with separately, as quite different experimental methods are required for each. 

From a mechanistic point of view, ion exchange reactions follow the hard and soft acids and bases (HSAB) principle. Materials containing the relatively soft imidazolium ion are therefore particularly efficient ion exchange materials for soft anionic species. For this reason, the measured distribution coefficients between the solid and liquid phases are often particularly high with soft anions and follow Hofmeister selectivity [142]. 

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Basic Extractants. Only long-chain quaternary ammonium salts, R3NCH3 X , ia which R represents Cg—0 2 groups and X nitrate or thiocyanate, are effectively used for REE separations (see Quaternary ammonium compounds). The extractant reacts with REE according to an anion-exchange reaction ... 

Complete the following reactions that take place for anion exchange reactions (weakly basis and strongly basis) ... 

In some cases only the first step is required, as with the formation of ethylam-monium nitrate. In many cases the desired cation is commercially available at reasonable cost, most commonly as a halide salt, thus requiring only the anion exchange reaction. Examples of these are the symmetrical tetraalkylammonium salts and trialkylsulfonium iodide. 

Interestingly, the specific environment of the ionic solvent system appears to activate the chiral Ni-catalyst beyond a simple anion-exchange reaction. This becomes obvious from the fact that even the addition of a 100-fold excess of Fi[(CF3S02)2N] or Na[BF4] in pure, compressed CO2 produced an at best moderate activation of Wilke s complex in comparison to the reaction in ionic liquids with the corresponding counter-ion (e.g., 24.4 % styrene conversion with 100-fold excess of Fi[(CF3S02)2N], in comparison to 69.9 % conversion in [EMIM][(CF3S02)2N] under otherwise identical conditions). 

Figure 15.4(A) shows the effect of the R = Zn2+/Al3+ ratio, which determines the charge density of the LDH layer, on the Freundlich adsorption isotherms. K values are far higher than those measured for smectite or other inorganic matrices. The increase in Kf with the charge density (Kf= 215, 228, 325mg/g, respectively, for R = 4, 3 and 2) is supported by a mechanism of adsorption based on an anion exchange reaction. The desorption isotherms confirm that urease is chemically adsorbed by the LDH surface. The aggregation of the LDH platelets can affect noticeably their adsorption capacity for enzymes and the preparation of LDH adsorbant appears to be a determinant step for the immobilization efficiency. [ZnRAl]-urease hybrid LDH was also prepared by coprecipitation with R = 2, 3 and 4 and Q= urease/ZnRAl from 1 /3 up to 2.5. For Q < 1.0,100 % of the urease is retained by the LDH matrix whatever the R value while for higher Q values an increase in the enzyme/LDH weight ratio leads to a decrease in the percentage of the immobilized amount.

Meyn, M., Beneke, K., and Legaly, G. Anionic-exchange reactions of layered double hydroxides, Inorg. 

Via Anion Exchange Reactions 10.1.3.1. Exchange of Chloride for Bromide... 

The anion-exchange reaction of the counterion in viologens is performed from the corresponding halides using an anion-exchange resin loaded with a given anion. 

The hydrido complex, [RhH(PPh3)3], is obtained in a number of anion exchange reactions of [RhCl(PPh3)3] due to hydride abstraction from the anions (equation 40). 

Apart from anion exchange reactions the complexes are inert. One of the few reagents to bring about a change in the coordination sphere is sulfur dioxide which coordinates to rhodium without displacement of a bidentate ligand. However, the product is not well characterized and the crystals contain clathrated sulfur dioxide.250... 

If [Rh(diphos)2]Cl is allowed to react with an anion exchange resin in the cyanide form, the corresponding cyanide complex (rc N 2089 cm-1) is formed. Upon dissolution of the product in benzene a diphos ligand is lost and [Rh2(CN)2(diphos)3] is formed.119 The dinuclear product probably contains a bridging diphos ligand (c/. [Cu2(N3)2(diphos)3]251). These reactions and the anion exchange reactions of [Rh(diphos)2]Cl are shown in Scheme 10a. 

Reaction of pyridine-N-oxides with triethyloxonium salt in methylene chloride or chloroform gives directly AT-alkoxy pyridinium salts with high yield. Quinolinium salts can also be prepared from the corresponding N-oxides [46], The synthetic procedure does not require the anion exchange reaction since triethyl oxonium salt possesses a non-nucleophilic counter anion, i.e. PFg ... 

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